1. Field of the Invention
Clutches are commonly used in various mechanical applications where it is desired optionally to connect or disconnect a rotating input member with a rotatable output load. One type of clutch utilized centrifugal force generated by rotation of the input member to move frictional members radially outwardly and into engagement with the output load, thereby to achieve a frictional connection between the two parts.
This invention relates to a centrifugal clutch and, more particularly, to electromagnetic means for interrupting a frictional driving connection between an input driving member and an output driven member at any time it is desired, regardless of speed of rotation of the clutched parts.
2. Description of the Prior Art
Various structures have been previously employed in clutch assemblies to effect a driving connection between an input member, usually a drive shaft, and an output member or load. U.S. Pat. No. 1,782,513 to Roos describes a centrifugal clutch in which the input member carries weighted pivot arms. Normally, coil springs urge the arms into contact with an output member, but at a predetermined rate of rotation of the input member, centrifugal force throws the weighted ends of the arms outwardly to interrupt the two frictionally joined parts.
U.S. Pat. No. 2,400,586 to Zimmermann describes a mercury actuated centrifugal clutch in which radially moveable members are forced into driving engagement with a driven member by the pressure of mercury contained in an expansible driving member chamber. This action occurs atuomatically upon rotation of the driving member.
The clutches of the two foregoing patents lack the advantages of electro-actuation or electro-deactuation of a driving frictional connection and are subject to still other shortcomings. As an example, making or breaking a driving connection between input and output members depends wholly upon the speed of rotation a certain member, usually the driving member. Further, as the springs of the Roos patent weaken, the desired moment of declutching is unavoidably varied. In the mercury-actuated clutch of the type described in the Zimmermann patent, difficulties arise in introducing the mercury into suitable container as well as sealing the container and preventing it from subsequent rupture, especially under the inertia and fluid pressure developed by the relatively heavy mercury under centrifugal force.
An electromagnetic clutch is disclosed by U.S. Pat. No. 2,606,638 to Russell which, however, is not of the centrifugal type. The magnetic circuit of this clutch includes a pair of radially disposed discs which are placed in parallel, close proximity. One disc is fixed to an input member, and the other disc is fixed to the output member. The flux of the electromagnetic circuit locks the two discs together. In this case, therefore, the electromagnetic circuit is used to effect the actual coupling of the two parts rather than their disconnection. Also, since this type of clutch is not of the centrifugal type, it has no components responsive to centrifugal force.